A phylogeny of the Leptostraca (Crustacea) with keys to families and genera

Abstract

A phylogenetic analysis of the Leptostraca Claus, 1880 is undertaken using 32 of the 41 known species (including 4 undescribed species). The value of outgroups for deriving a plausible phylogeny in a group whose affinities remain contentious is discussed. A hypothetical ancestor is considered the best solution to the problem and states were scored based on general principles of crustacean evolution as evidenced by a wide variety of taxa. States of the 43 characters used in the analysis are detailed. The new phylogenetic hypothesis is compared with those of Olesen (1999). We conclude that a phylogeny based on species-level taxa and many informative characters is more likely to represent true evolutionary relationships than one based solely on genera and few characters. A new classification based on the phylogeny is derived with a new family, Paranebaliidae, being erected for Paranebalia Claus, 1880 and Levinebalia Walker-Smith, 2000. Nebaliopsididae Hessler, 1984 is supported for Nebaliopsis Sars, 1887. A restricted Nebaliidae Samouelle, 1819 for the remaining genera (Speonebalia Bowman, Yager and Iliffe, 1985, Nebaliella Thiele, 1904, Dahlella Hessler, 1984 and Nebalia Leach, 1814). Sarsinebalia Dahl, 1985 is synonomised with Nebalia. New keys and family andgeneric diagnoses are presented. All known species are listed with notes on distribution.